elm leafminer

(Fenusa ulmi)

Conservation Status
elm leafminer
  IUCN Red List

listed

     
  NatureServe

listed

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Elm leafminer is a very small common sawfly. It is native to eastern Europe and Scandinavia. It was brought to North America most likely on imported elms. It now occurs in the United States from New England to the upper Midwest, in the Pacific Northwest, and in southeast Canada. Based on the scarcity of reports, it is still relatively uncommon in Minnesota.

Adults are small, about (4 mm) long, and dark colored. More detailed information about the adult is not available.

Due to the small size of the adult, elm leafminer is most often identified by the damage the larva causes to its host plant. Mines are seen from mid-May to early June on American elm and slippery elm. The larva feeds between the upper and lower surfaces of the leaf. It creates a serpentine mine at first. That soon develops into a small blotch between two lateral veins, later into a large blotch on one side if the midrib. The mines are clear and the flattened, whitish-green or yellowish-white larva can be seen when viewing the upper side of the leaf. The frass can also be seen within the mine. It appears as long, connected chains at first, later as loose grains. The infected part of the leaf turns brown and eventually falls off. A heavy infestation may cause the entire tree to defoliate, but the infected tree flushes again and survives.

 
     
 

Size

 
 

Total Length: about (4 mm)

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

Elms

 
     
 
Biology
 
 

Season

 
 

One generation per year: Mid-March to mid-April

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

Adults emerge from mid-March to mid-April, depending on the temperature and coinciding with opening of elm leaf buds. The adults are all female. Males are rare in Europe and have not been found in North America. Eggs develop into embryos without first being fertilized by sperm (parthenogenesis). The female begins laying eggs immediately after emerging. She creates a slit in the upper surface of a leaf into which she deposits a single egg. At first, eggs are laid near leaf veins. Later they are placed anywhere on the leaf. The eggs hatch in about ten days. Each larva passes through five stages (instars), then drops to the ground and burrows into the soil. It then forms a thin, papery cocoon, where it remains in the pupal stage through summer, fall, and winter.

 
     
 

Larva Food

 
 

Leaves of elm trees, including American elm and slippery elm

 
     
 

Adult Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

7, 29, 30.

 
  11/9/2019      
         
 

Occurrence

 
 

Uncommon

 
         
 
Taxonomy
 
 

Order

Hymenoptera (ants, bees, wasps, and sawflies)  
 

Suborder

Symphyta (horntails, sawflies)  
 

Superfamily

Tenthredinoidea (sawflies)  
 

Family

Tenthredinidae (common sawflies)  
 

Subfamily

Heterarthrinae  
  Tribe Fenusini  
 

Genus

Fenusa  
       
 

Synonyms

 
 

Kaliosysphinga ulmi

 
       
 

Common Names

 
 

elm leafminer

 
       

 

 

 

 

 

Glossary

Instar

The developmental stage of arthropods between each molt; in insects, the developmental stage of the larvae or nymph.

 

 

 

 

 

 

       
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MinnesotaSeasons.com Photos
   
  elm leafminer   elm leafminer
       

 

Camera

     
Slideshows
   
  Fenusa ulmi
Ian Andrews
 
  Fenusa ulmi  
     

 

slideshow

       
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Other Videos
 
  Elm Leaf Miner Clip
Sam Benvie
 
   
 
About

Oct 31, 2014

   
       

 

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Created: 11/9/2019

Last Updated:

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